/Engine/Source/Runtime/UMG/Public/Blueprint/WidgetBlueprintLibrary.h
Given the pointer event, emit the DetectDrag reply if the provided key was pressed. If the DragKey is a touch key, that will also automatically work.
static [FEventReply](API\Runtime\UMG\Components\FEventReply) DetectDragIfPressed ( const [FPointerEvent](API\Runtime\SlateCore\Input\FPointerEvent) & PointerEvent, [UWidget](API\Runtime\UMG\Components\UWidget) * WidgetDetectingDrag, [FKey](API\Runtime\InputCore\FKey) DragKey )